U.S. patent number 7,284,898 [Application Number 10/797,220] was granted by the patent office on 2007-10-23 for system and method for mixing water and non-aqueous materials using measured water concentration to control addition of ingredients.
This patent grant is currently assigned to Halliburton Energy Services, Inc.. Invention is credited to Keith E. Blaschke, Alan B. Duell.
United States Patent |
7,284,898 |
Duell , et al. |
October 23, 2007 |
System and method for mixing water and non-aqueous materials using
measured water concentration to control addition of ingredients
Abstract
The present invention is directed to a system and method for
mixing a fluid comprising water and at least one non-aqueous
material. The system comprises a mixing tub and mixing head adapted
to inject the fluid into the mixing tub. It also includes a
plurality of lines connected to the mixing head that supply the
mixing head with water and the at least one non-aqueous material
and a recirculation circuit that delivers the fluid from the mixing
tub back to the mixing head. The system further includes a sensor
connected to the recirculation circuit that measures the
concentration of water in the fluid. An automatic controller uses
the concentration measurement data to control the amount of each of
the ingredients injected into the mixing tub.
Inventors: |
Duell; Alan B. (Duncan, OK),
Blaschke; Keith E. (Duncan, OK) |
Assignee: |
Halliburton Energy Services,
Inc. (Duncan, OK)
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Family
ID: |
34919998 |
Appl.
No.: |
10/797,220 |
Filed: |
March 10, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050201197 A1 |
Sep 15, 2005 |
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Current U.S.
Class: |
366/152.1;
366/136 |
Current CPC
Class: |
B01F
3/1221 (20130101); B01F 5/106 (20130101); B01F
7/167 (20130101); B01F 7/18 (20130101); B01F
15/0022 (20130101); B01F 15/00344 (20130101); B01F
15/0408 (20130101) |
Current International
Class: |
B01F
15/02 (20060101) |
Field of
Search: |
;366/131-132,134,136-137,152.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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19 21 681 |
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Nov 1970 |
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DE |
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0 419 281 |
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Mar 1991 |
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EP |
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402171213 |
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Jul 1990 |
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JP |
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3-10662 |
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Jan 1991 |
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JP |
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WO 02/44517 |
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Jun 2002 |
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WO |
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Other References
DE 1921681 and English translation. cited by examiner .
SPE 71402 paper entitled "Innovative Solution For Cementing Across
Formations With Very Low Fracture Gradients" by Christian Hun et
al., 2001. cited by other .
Article entitled "Light as a Feather, Hard as a Rock" by Abdullah
Al-Suwaidi et al., pp. 2-15, Oilfield Review, Summer 2001. cited by
other .
Foreign communication from related counterpart application dated
Jul. 15, 2005. cited by other.
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Primary Examiner: Cooley; Charles E.
Attorney, Agent or Firm: Wustenberg; John W. Baker Botts,
L.L.P.
Claims
What is claimed is:
1. A system for preparing a mixture of water and at least one
non-aqueous material, comprising: a mixing zone; wherein the mixing
zone comprises a mixing tub; means for injecting water into the
mixing zone; means for injecting the at least one non-aqueous
material into the mixing zone; and a sensor disposed within the
mixing tub that measures the concentration of water in the
mixture.
2. The system for preparing a mixture according to claim 1, wherein
the injecting means further comprises a mixing head into which the
water and at least one non-aqueous material are injected prior to
being injected into the mixing zone and a flow line having a valve
disposed therein that injects the water into the mixing head and a
flow line having a valve disposed therein that injects the at least
one non-aqueous material into the mixing head.
3. The system for preparing a mixture according to claim 2, wherein
each of the valves is manually controlled.
4. The system for preparing a mixture according to claim 2, wherein
each of the valves is controlled by an automatic controller, which
is connected to the water concentration sensor.
5. The system for preparing a mixture according to claim 4, wherein
each of the valves comprises an actuator connected to the automatic
controller.
6. The system for preparing a mixture according to claim 5, further
comprising a flow rate sensor disposed within the water flow line
and wherein the flow rate sensor is connected to the automatic
controller.
7. The system for preparing a mixture according to claim 6, wherein
the automatic controller controls one or more of the actuators on
the valves in response to signals received from the water
concentration sensor and the flow rate sensor.
8. The system for preparing a mixture according to claim 5, wherein
the automatic controller controls one or more of the actuators on
the valves in response to signals received from the water
concentration sensor.
9. The system for preparing a mixture according to claim 4, wherein
the automatic controller comprises a computer.
10. The system for preparing a mixture according to claim 1,
wherein the mixing tub comprises two compartments separated by a
weir.
11. The system for preparing a mixture according to claim 10,
further comprising an agitator in each of the compartments that
mixes the water and at least one non-aqueous material.
Description
FIELD OF THE INVENTION
The present invention relates generally to systems for preparing a
mixture of a water and at least one non-aqueous material, and more
particularly to a system and method for batch and continuous mixing
of such materials using measured water concentration to control the
addition of ingredients.
BACKGROUND OF THE INVENTION
In the drilling of oil and gas wells, it is often necessary to
place cement or some other material around the outside of casing to
protect the casing and prevent movement of formation fluids behind
the casing. The cement is typically mixed in a mixer at the surface
and pumped down hole and around the outside of the casing. The
mixing is typically done by combining the cement ingredients,
typically water, cement, and other non-aqueous materials until the
proper density is obtained, and then continuing to mix as much
material as needed at that density while pumping down hole in a
continuous process. The process has been automated by most service
providers so that automatic controls maintain the proper density
during mixing. Density is of importance because the resulting
hydrostatic pressure must be high enough to keep pressurized
formation fluids in place but not so high as to fracture a weak
formation. However, density is only one of several properties
important to a cement slurry. Typical slurry densities range from
14 ppg (lbs/gal.) to 20 ppg.
In recent years, more need has arisen for light-weight slurries
that can be used in wells with low fracture gradients, i.e., in
formations that cannot support high hydrostatic pressures. These
slurries may range in weight from 11 ppg to less than the density
of water, which is 8.33 ppg. One method for making light-weight
slurries is to add low specific gravity non-aqueous materials such
as hollow glass beads to the dry materials to decrease the density.
A drawback with such slurries is that below certain densities, the
ratio of non-aqueous material to water can change significantly
with only minor changes in density. Changes in the non-aqueous
material-to-water ratio can affect slurry viscosity, compressive
strength, and other properties. In these situations, density-based
control systems do not work well.
Recent developments in processes to mix these light weight slurries
involve the measurement of volumes rather than density in order to
ensure the proper proportion of non-aqueous materials and liquids.
This is done by measuring the volume of all liquids going into and
out of the mixing tub using, e.g., a volumetric flow meter and also
measuring the tub level. The volume of non-aqueous materials added
to the mixing tub is not measured, but rather is calculated from
the liquid volume and level measurements. The amount of non-aqueous
materials and liquids in the mixture can thus be determined and
hence controlled. Examples of this type of system are described in
U.S. patent application Ser. No. 2002/0093875 A1 and International
Patent Application No. WO 02/44517 A1. A system that purports to
better control the density of slurries is also described in U.S.
Pat. No. 5,775,803.
While the above described volumetric mixing systems generally work
well, they have the disadvantage of adding equipment and flow lines
to the mixing systems. Additionally, new control algorithms are
needed to monitor the measurements and control the process. In many
applications, particularly offshore, space is not available for the
additional equipment. These systems also become less accurate as
the size of the mixing tub increases, sometimes limiting their
application.
SUMMARY OF THE INVENTION
The present invention is directed to a system and method that
eliminates or at least minimizes the drawbacks of prior volumetric
mixing systems.
In one aspect of the invention, the present invention is directed
to a system for preparing a mixture, such as a cement, comprising
water and at least one non-aqueous material. The system comprises a
mixing zone; means for injecting water into the mixing zone; means
for injecting the at least one non-aqueous material into the mixing
zone; and a sensor disposed within the mixing zone that measures
the concentration of water in the mixture. In another embodiment,
the system according to the present invention comprises a mixing
zone; means for injecting water into the mixing zone; means for
injecting the at least one non-aqueous material into the mixing
zone; a flow line through which the mixture is discharged from the
mixing zone; and a sensor disposed within the discharge flow line
that measures the concentration of water in the mixture.
In another aspect of the present invention, the present invention
is directed to a method for preparing a mixture comprising water
and at least one non-aqueous material. The method comprises the
steps of combining the water and at least one non-aqueous material
in a mixing zone; measuring the concentration of water in the
mixture; and adjusting the amount of water and/or at least one
non-aqueous material being combined in the mixing zone so as to
obtain a desired water/non-aqueous material concentration. In
another step, the mixture is discharged from the mixing zone. The
concentration of water in the mixture may be measured either in the
mixing zone or as the mixture is being discharged from the mixing
zone.
The system and method according to the present invention has
application in either a batch mixing process or a continuous mixing
process. In a batch process, a tub of any volume can be mixed to
the proper ratio of water and non-aqueous material, and then
discharged. To accomplish a continuous mixing process, the mixing
tub is initially filled with a mixture that has the proper ratio of
water and non-aqueous material (solid or liquid) as measured by the
concentration sensor. Then the mixture can be discharged from the
mixing tub while simultaneously adding new ingredients to the
mixing tub in a controlled manner that maintains the ratio of water
and non-aqueous material in the tub, thus maintaining a continuous
process. A continuous process allows the mixing of large volumes
using a small mixing tub.
The advantages of measuring the water concentration directly
include reduced pieces of operating equipment, smaller space
required for operating equipment, lower cost, and simplified
controls. The present invention thus provides a system that is less
expensive and easier to retrofit on existing equipment. Additional
features and advantages of the present invention will be readily
apparent to those skilled in the art upon a reading of the
description of the exemplary embodiments, which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the present disclosure and
advantages thereof may be acquired by referring to the following
description taken in conjunction with the accompanying drawings,
which:
FIG. 1 is a schematic diagram of a system for mixing a fluid
comprising water and at least one non-aqueous material in
accordance with the present invention.
FIG. 2 is block diagram for an automatic control system for
controlling the mixing system of FIG. 1.
FIG. 3 is a schematic diagram of an alternate embodiment of the
system shown in FIG. 1.
FIG. 4 is a block diagram of an automatic control system for
controlling the mixing system of FIG. 3.
FIG. 5 is a flow diagram illustrating the steps in a process of
mixing a fluid comprising water and at least one non-aqueous
material in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The details of the present invention will now be described with
reference to the accompanying figure. Turning to FIG. 1, a system
for mixing a fluid comprising water and at least one non-aqueous
material is referred to generally by reference numeral 10. The
system 10 comprises a mixing tub 12 and a mixing head 14. The
mixing tub 12 has two compartments 16 and 18, which are separated
by a weir 20. The mixing head 14 is placed over the first
compartment 16, which is referred to as the pre-mix side. The fluid
mixture, or slurry, is discharged from the second compartment 18,
which is referred to as the down-hole side.
In one certain embodiment, the mixing head 14 is a Halliburton RCM
II, RCM IIe, or RCM IIIr mixing head. As those of ordinary skill in
the art will appreciate, however, other suitable mixing heads can
be used. In its simplest embodiment, the mixing head 14 has three
input ports for receiving inputs from flow lines 22, 24, and 26,
respectively. However, as those of ordinary skill in the art will
appreciate, the mixing head 14 may be adapted to receive inputs
from additional flow lines.
Referring now to each individual flow line, flow line 22 is
provided for injecting water into the mixing head 14. Water enters
flow line 22 from an external source, such as a storage tank or
other type of reservoir (not shown). In one certain exemplary
embodiment, a flow rate sensor 28 is disposed within flow line 22.
As those of ordinary skill in the art will appreciate, the flow
rate sensor 28 can either be a volumetric flow meter or a mass flow
meter or other similar known device. An actuator-controlled valve
30 may also be disposed within flow line 22 for controlling the
amount of water being injected into the mixing head 14.
Alternatively, a manually-controlled valve can also be used.
Flow line 24 is provided for injecting a non-aqueous material, such
as a dry cement into the mixing head 14. The non-aqueous material
is stored in a bulk storage tank or other type of reservoir (not
shown). An actuator-controlled valve 32 may also be disposed within
flow line 24 for controlling the amount of non-aqueous material
being injected into the mixing head 14. Alternatively, a
manually-controlled valve can also be used. Finally, flow line 26
injects recirculated fluid mixture into the mixing head 14. The
recirculated fluid mixture is drawn from the first compartment 16
in the mixing tub, as will be further described below.
The system 10 further comprises a recirculation circuit 40. The
recirculation circuit 40 comprises flow lines 42 and 26. Flow line
42 is connected at one end to a discharge port formed at the bottom
of the first compartment 16 of the mixing tub 12. It is connected
at the other end to an input port of a pump 46, which in one
certain exemplary embodiment is a centrifugal pump. The flow line
26 is connected at one end to an output port of pump 46 and at the
other to in input port of the mixing head 14. The recirculation
circuit 40 further comprises a sensor 48, which measures the
concentration of water within a fluid. The sensor 48 is disposed in
flow line 26. However, as those of ordinary skill in the art will
appreciate, the sensor 48 can also be disposed in discharge flow
line 45 or elsewhere in the system where the mixture is present,
such as the mixing tub 12. In one certain exemplary embodiment, the
water concentration sensor is a Micro-Fluid LB 455 manufactured by
Berthold Technologies. This sensor determines the amount of free
water in a mixture by passing microwaves through the mixture and
measuring phase shift and attenuation. It is capable of providing a
process signal proportional to the water concentration or dry mass
of the fluid mixture.
The system 10 further comprises a valve 44 disposed in flow line
45, which discharges the fluid mixture from the second compartment
18 of the mixing tub 12. The valve 44 can be either manually
operated or actuator controlled, e.g., if used in an automated
system. System 10 may further comprise agitators 47 and 49 disposed
in each of the compartments 16 and 18, respectively. Agitators 47
and 49 can further assist/enhance the mixing of the fluid.
The present invention further includes an automatic controller 50,
which is shown in block form in FIG. 2. At the core of the
automatic controller 50 is a computer 52, which takes input
readings from the water concentration sensor 48 and flow rate
sensor 28. Sensors 28 and 48 are connected to computer 52 via
electric cables 54 and 56, respectively. The output of sensor 28 is
a process signal indicative of either the volume or mass of water
flowing through flow line 22. The output of sensor 48 is a process
signal indicative of either the concentration of water or
non-aqueous material flowing through flow line 26.
Computer 52 takes these readings and generates process control
signals, which activate one or both of the actuators on the valves
30 and 32 via electric cables 58 and 60, respectively. The computer
52 compares the actual concentration of water or non-aqueous
material in the fluid mixture to the desired amount and adjusts the
amount of ingredients being added to the mixture accordingly. The
rate at which non-aqueous material enters the mixing head 14 is not
measured, but the rate is adjusted and controlled based on
measurements from the water concentration sensor 48.
For example, if the concentration has too much water, the computer
52 may either reduce the amount of water being injected into the
mixing head 14 or increase the amount of non-aqueous material being
added or a combination of both. The computer 52 can use a PID
(proportional integral derivative) control algorithm based program
to control this operation or other similar program. As those of
ordinary skill in the art will appreciate, the automatic controller
50 can utilize several different types of equipment. In one certain
exemplary embodiment, a Halliburton UNIPRO II controller is
used.
In one certain embodiment, the centrifugal pump 46 is manually
operated. In another embodiment, it is controlled by the computer
52 via electric cable 62, as shown in FIGS. 2 and 4. In another
embodiment, agitators 47 and 49 are manually operated. In another
embodiment, they are controlled by computer 52 via electric cables
59 and 61, as shown in FIGS. 2 and 4. In yet another embodiment,
valve 44 is manually controlled. In still another embodiment, it is
controlled by computer 52 via electric cable 63.
In one certain exemplary embodiment, the system 10 incorporates a
water concentration sensor into a system similar to Halliburton's
RCM recirculating mixing system. The RCM mixing system is disclosed
in U.S. Pat. Nos. 3,563,517; 5,027,267; 5,046,855; and 5,538,341,
which are hereby incorporated by reference. The RCM mixing system,
as presented in these patents, incorporates a densometer, also
known as a densitometer, and controls the mixing process based on
density. In the present invention, the densometer is replaced with
the water concentration sensor and the mixing process is controlled
based on water or non-aqueous material concentration.
Alternatively, both the densometer and water concentration sensor
could be included in such a way that either or both devices could
be used for control. Such an alternate embodiment is shown in FIGS.
3 and 4, which adds densometer 64 to flow control line 26. Electric
cable 66 connects densometer 64 to the computer 52.
The method or process for mixing a fluid containing water and at
least one non-aqueous material in accordance with the present
invention will now be described with reference to the flow chart in
FIG. 5. In step 100, the process is started. In step 110, the
amount of water needed to make a mixture that will fill the first
compartment 16 of the mixing tub 12 is added to the pre-mix side.
In step 120, the contents of the first compartment 16 are then
circulated through the recirculation circuit 40, and thus through
the water concentration sensor 48. In step 130, non-aqueous
material is added until the concentration of water (or non-aqueous
material) in the mixture is at the desired value, as measured by
the sensor 48. In step 140, water is continuously added through the
mixing head 14 while simultaneously adding the non-aqueous
material. The rate at which water is added is controlled to a
pre-determined rate based on the rate at which the mixture, e.g.,
cement slurry is needed. The rate at which non-aqueous material is
added is adjusted to maintain the proper water (or non-aqueous
material) concentration as measured by the sensor. As water and
non-aqueous material are added, the volume of mixture increases
until it flows over the weir 20 into the second compartment 18 from
which it can be discharged. Typically, in oil well applications the
discharge would go to a pump (not shown), which would pump it down
hole. The process is ended at step 150.
As should be evident to a person of ordinary skill in the art, the
above process can be fully or partially automated, or not automated
at all. In one example, activation of the pump 46 would not be
automated, nor would activation of the discharge valve 44, agitator
47 and agitator 49. As pointed out above, activation of valves 30
and 32 can also be manual. In another embodiment, all the functions
are automated, as shown in FIGS. 2 and 4.
As those of ordinary skill in the art will appreciate, the present
invention has numerous applications. One such application is the
mixing of oil field cement slurries. Other applications include,
but are not limited to, the mixing of drilling fluids, fracturing
fluids, and emulsions of water and non-aqueous liquids.
Furthermore, many types and styles of mixers are known in the oil
and gas industry, and many more can be conceived. Thus, this
invention can be applied to other mixers and systems, as would be
evident to those skilled in the art. Accordingly, while the
invention has been depicted, described, and is defined by reference
to exemplary embodiments of the invention, such a reference does
not imply a limitation on the invention, and no such limitation is
to be inferred. The invention is capable of considerable
modification, alteration, and equivalents in form and function, as
will occur to those ordinarily skilled in the pertinent arts and
having the benefit of this disclosure. The depicted and described
embodiments of the invention are exemplary only, and are not
exhaustive of the scope of the invention. Consequently, the
invention is intended to be limited only by the spirit and scope of
the appended claims, giving full cognizance to equivalents in all
respects.
* * * * *